A flat panel display, such as a liquid crystal display and an organic light emitting display, has a structure which forms a thin film transistor (hereinafter describe as “TFT”) and a display circuit on a substrate such as glass. However, according to a recent request of an increase in size and in definition of the thin-screen television, a display panel having a large scale and high-definition has been required equally to a display panel using this type of TFT (TFT panel).
Conventionally, as a wiring film, such as a gate electrode, source electrode and drain electrode of TFT panel having a large scale and high-definition, it was conventional to use a wiring film which is formed of aluminum based materials. However, recently, the use of a wiring film formed of copper (Cu) based materials having a higher electrical conductivity than aluminum (Al) has been promoted for lowering in resistance of a wiring film.
As a copper based materials used for a wiring film of the TFT panel, a variety of copper alloys are proposed, and for example, in Patent Document 1 or Patent Document 2 shown below, Cu—Ca alloy have gotten attention recently. A wiring film formed of Cu—Ca alloy is not only lower in specific resistance than (a wiring film formed of) Al based materials, but also is more excellent in adhesion properties between the wiring film and the substrate such as the glass than a wiring film formed of Al based materials. In addition, in a case where a wiring film of the TFT panel is formed by this type of Cu—Ca alloy, sputtering is applied normally, and in this case, a sputtering target formed of Cu—Ca alloy is used.
In addition, in Patent Document 3 shown below, in a sputtering target formed of Cu—Ca alloy, a target as defined in a range of 10 to 50 μm of an average particle size of Cu—Ca based crystallized product is shown in order to suppress the occurrence of abnormal discharge during sputtering.